The development of oil fields worldwide is accompanied by flaring of a natural gas which results in lost revenue. In addition to this loss, the wasted gas is accompanied by a sizeable amount of pollutants (e.g., methane and carbon dioxide) that are released to the atmosphere. Presently, there is no efficient way of capturing these gases. The World Bank estimates that 140 billion m3 of natural gas are flared annually, an amount equivalent to 20% of the U.S. annual gas consumption.
Currently, there is no fully developed economically effective method for capturing the release gases at isolated wells. Although gas collection seems to be an obvious strategy, gas collection requires an infrastructure of pipelines and compressor stations that are too costly to construct and maintain. Moreover, extracting liquefiable C3+ components only makes a minor improvement to the problem since methane in general cannot be collect. Indeed, methane usually accounts for more than 75% wt. of the uncollected natural gas.
Partially oxidation processes provide a potential method for recapturing alkanes and in particular, methane. Currently, direct homogeneous partial oxidation (DHPO) produces a variety of oxygenates such as alcohols and aldehydes, and carboxylic acids in smaller concentrations. Conversion of these liquid products into higher value fuels and chemicals via process integration is of great interest since process integration permits for cost reduction and therefore applicability at smaller scale. Increasing the carbon length of the alkane feed gas to partial oxidation processes is known to produce higher proportions of alcohols, aldehydes and carboxylic acids having a carbon length greater than one carbon. Many of these components have relative volatilities at standard temperature and pressure similar to that of water thereby complicating separations with conventional techniques. Furthermore, formaldehyde reversibly forms methylene glycol and hemi-formal polymers that can interfere with recovery of high boiling alcohols. The unseparated blend which typically includes water, methanol, formaldehyde, ethanol, acetone, isopropanol, acetaldehyde, formic and acetic acids, and corresponding acetals and esters has little direct value as a fuel in internal combustion engines. Traditional means of separating this blend into individual components and thereby upgrade its fuel and chemical value has been problematic as is known to those skilled in the art.
The prior art separation schemes for blended oxygenates tend to be complicated. For example, azeotropic distillation to separate blends of partially oxidized products. Azeotropic distillation involves complexity relating to the use of additional solvents, higher flow rates, and additional vessels. Therefore, these separations are wasteful from both a capital and operational expense perspective. U.S. Pat. No. 2,710,829 details a method to separate a mixture of alcohols, aldehydes, ketones, and esters. This patent describes a process that uses over ten columns, many of which include azeotropic distillations, to separate the individual oxygenate components. These capital intensive distillation schemes are a primary reason that acetic acid formed by carbonylation of methanol is favored over butane oxidation. (Arpe, H. J. et al, Industrial Organic Chemistry 5th ed. (2010) p. 183). Moreover, even after separation from the partial oxygenate blend, mixed alcohols have limited marketability. For example, methanol is currently of lower value on a weight basis.
Accordingly, there is a need for improved methods for processing blends of partially oxygenated compounds into products that have improved value as a fuel.